Chronic wounds such as venous ulcers which do not heal, represent a serious problem to sufferers and healthcare providers. The prevalence of active venous ulcers in the adult population is high and their treatment is very costly to healthcare services. A venous ulcer is an area of damage to the skin that fails to heal after several weeks. They occur when the veins and muscles in the lower legs are weak and cannot efficiently pump the blood back to the heart as a result of damaged valves. Gravity then causes the blood to pool in the lower legs. The pooling blood eventually leaks out of the veins and into the surrounding tissue causing the tissue to swell which then leads to wounds and ulcers. Such wounds may be extremely painful and grow to a considerable size. Applying increased external pressure to the legs with compression bandaging or graduated compression hosiery, for example, has been used to assist in the healing of venous leg ulcers and gravitational eczema. The increased pressure forces the blood back into the veins creating an improved blood flow thereby allowing the ulcers to heal. Compression bandages or graduated compression hosiery apply pressure to the leg, with greater pressure near the ankle and reduced pressure higher up. This forces the blood to keep circulating away from the lower leg.
Studies have shown that the process of healing, growth and regeneration in living tissue is brought about by the flow of endogenous electrical current. It has been suggested that the application of external microcurrents to injured tissue can assist the body's natural healing process by augmenting the flow of current through the injured tissue. The application of electrical signals to injured tissue as a form of therapy is known as electrotherapy and has been described in various publications.
U.S. Pat. No. 4,982,742 describes a method and apparatus for facilitating the healing of soft tissue wounds involving the application of a single bi-phase microcurrent waveform to a selected area of tissue. The waveform is characterised by a frequency ranging from 10 to 50 Hz and an amplitude ranging between 100 and 1000 μA. The waveform is delivered by a disposable bandage containing an integrated circuit and power source.
Similarly the method described in U.S. Pat. No. 6,393,326 uses one waveform throughout treatment. The electrical treatment signal disclosed in this document is characterised by a bipolar voltage waveform at a frequency of between 2 Hz and 10 Hz. This method is particularly adapted to the treatment of bedsores which are known to have substantially zero electrical activity.
EP367320 also relates to a system for the treatment of wounds by electric stimulation.
The document discloses a waveform generator adapted to generate either a direct current signal or a pulsed signal comprising pulses with a pulse width of less than 1 ms. It further discloses that optimal pulse width is about 0.1 ms. The DC current application is believed to produce wound healing and the pulse signals when applied directly into the wounds are said to produce a pain-relief effect.
None of the above methods is specifically adapted to the treatment of venous ulcers. In addition, all of the above described methods are applied on their own and are not used simultaneously with other methods of wound healing
There is therefore a recognised need for an effective method for promoting the healing of chronic wounds such as venous ulcers. It would be particularly advantageous to have a method of electrotherapy tailored to the healing of venous ulcers.